Project Summary/Abstract Aging negatively impacts muscle mobility and function within the head and neck. In tongue muscles, aging is associated with a reduction in tongue force generative capacity that can negatively impact an older individual's ability to safely swallow during mealtimes. Swallowing impairment, also known as dysphagia, negatively impacts a person's quality of life and physical health. Dysphagia is linked to increased risk of aspiration which increases morbidity and mortality. Considering the rapidly growing population of people over the age of 65, treating dysphagia is critical to promote adequate health outcomes and reduce the financial burden of this condition. Current treatments for dysphagia may involve tongue strengthening exercises. While these exercises are routinely prescribed to patients, the current optimal dose necessary to effectively treat age- related tongue weakness is not known. Dose of exercise is an important factor to consider when developing a therapy regimen, and finding the minimally effective dose is necessary to ensure patient adherence to achieve desired results. We propose to study this treatment using a well-developed animal model of aging in order to examine the effects of dose on biologically meaningful variables related to tongue muscle structure and resulting swallowing function. The proposed research will use a well-developed rat model of aging to examine the effects of varied doses of tongue exercise (control, 1 day/week, 3 days/week, 5 days/week) on tongue muscle morphology (muscle fiber type and size) and metabolism (mitochondrial content and function) related to swallowing function. The hypothesis of this study is that the minimum dose for effecting biological change in tongue muscles will result in significantly improved swallowing function. Further, exercise doses larger than the minimum effective dose identified in this research will not deliver substantially improved swallow function. This work has 3 specific aims: (1) To quantify the minimum dose of tongue exercise effective in mitigating age-related changes in tongue force and resulting swallowing function; (2) To determine how different doses of tongue exercise affect age-related changes in morphology of tongue muscles and how these variables relate to swallowing function; (3) To determine how different doses of tongue exercise affect age-related changes in mitochondrial content and function in tongue muscles and how these variables relate to swallowing function. The proposed research is important and significant in developing appropriate protocols for tongue-exercise therapy to be used clinically. Understanding the impact of dose on tongue biology, metabolism, and swallowing function are necessary to develop evidence-based and ethical foundations for what is prescribed for use in people with swallowing impairment.